I. Field of the Invention
The present invention relates generally to turbochargers and, more particularly, to a turbocharger with a system for insulating the heat of the turbine of the turbocharger from the bearing housing and the bearing assemblies.
II. Description of the Prior Art
For nearly 30 years, general aviation turbocharged piston engines have been boosted with slightly modified automotive-type turbochargers Although durable and reliable, this type of turbomachinery has seen little change since its introduction and continues to reflect weight and performance characteristics of ground equipment.
A particular impediment toward lighter turbochargers has been the prohibition against utilizing lighter components While a number of components may be fabricated from lightweight materials, certain components have remained limited to composition from heavy metals.
Perhaps the most important component which conventionally defies conversion to a lightweight material is the bearing housing. The bearing system is located inboard of the compressor and turbine housings and includes therein one or more bearing assemblies. Because the high exhaust gas heats to which the turbine wheel and associated elements are exposed sometimes reach over 1650.degree. F., bearing housings are conventially composed of ductile iron. Some are even water cooled. Either way, known constructions translate into a substantial weight penalty.
The potential heat transfer to the bearing housing, the bearing assemblies and the lubricating oil contained therein presents a problem which has long remained unsolved. Because of this high heat, aluminum has not been a practical alternative.